GB 2 081 377 A discloses a water vaporiser device for supplying steam to the air intake of a diesel or petrol engine having an exhaust system, the water vapouriser device comprising:
a water boiler in heat exchange relation with the exhaust system of the engine, and
a steam reservoir having a steam inlet arranged to receive steam from the boiler, an air inlet, and an outlet arranged to supply steam to the air intake of the engine.